The present invention pertains to the radio communication art and, more particularly, to a multisectored antenna receiving system.
Several types of sectored antenna receiving systems have been developed for application in the radio communication art. Sectored antenna systems are commonly used in applications wherein the remote transmitter whose signal is to be received may be positioned in any one of multiple locations. Thus, such systems are normally designed in moving vehicle type applications. By using a sectored antenna array, as opposed to, for example, an omnidirectional antenna, signal to noise performance can be significantly enhanced thus producing a superior communication system.
While numerous sectored antenna scanning systems are known in the prior art, a particularly effective one is that described in U.S. Pat. No. 4,101,836, issued July 18, 1978, entitled "Sectored Antenna Receiving System", invented by Timothy Craig and James Stimple, and assigned to the same assignee as the instant application.
In the above referenced antenna scanning system control logic causes an antenna switch to sequentially couple each of a plurality of antenna sectors to a receiver. The signal level produced by each antenna is detected in appropriate circuitry and, if the detected signal levels for the one or more sectors exceeds a threshold level the control logic causes the antenna switch to scan the sectors in various predetermined modes.
A problem with such prior art scanning systems, and notably of the system referenced above, is that at the instance of antenna switching energy from off channel signals is translated to the desired channel and processed by the receiver's tuned circuits, thereby creating a transient, or spurious response. If allowed to pass to the control logic, this spurious response will be treated as a sector received signal. Thus, the system is subject to falsing.
One solution to the tuned stage generated transient signal problem is to reduce antenna switching times to the point whereby the generated transients are of insignificant magnitude. This solution has proven undesirable in applications wherein rapid antenna scanning is required.